Technical Field
The present invention relates to an insulation degradation monitoring device which monitors a degradation state of an insulator supporting a charging portion of an electric instrument such as a power switchboard or the like.
Background Art
In an inner portion of a heavy electric instrument such as a power switchboard, there exist bus lines as well as many high-voltage charging portions of a main circuit instrument and the bus line and the high-voltage charging portions are supported at a grounding portion side by an insulator. The insulator is used during a long period in a state where the high-voltage charging portions are supported by the insulator, whereby an insulation capability is deteriorated, and a leakage electric current, which is flowed from a charging portion side through the insulator to the grounding portion side, is increased. When an inclement of the leakage electric current is left, the degradation of the insulator is more advanced, and the leakage electric current is a generation factor of a ground fault in a worst case. In order to previously prevent the ground fault, it is required that a degradation state of the insulator is monitored, and the insulator is replaced at a suitable period. Suitable replacement timing is required for effective operation of an electric power receiving and transforming facility.
As a conventional art for detecting a degradation degree of an insulator in an electric power receiving facility, for example, there is a known art by which dust in an electric power receiving panel is collected, and a surface resistivity of the insulator is calculated in accordance with a value of an ion, which is included in the dust, a temperature and a humidity history, and moreover, a remaining life of the insulator is estimated in accordance with a threshold value which is determined in accordance the surface resistivity of the insulator and a surface resistivity of a new insulator, a usage lapse age of the insulator, and an amount of the dust, whereby a suitable replacement timing is decided (for example, refer to Patent Document 1).
Moreover, there is a known art by which an electric conductor is provided at an interphase portion of an insulation frame, in which a three-phase vacuum circuit breaker is installed, and the electric conductor is connected to a grounding metal, and a leakage electric current, which is passed through the outside or the inside of the insulation frame and is flowed to an interphase portion of a charging portion in accordance with an insulation degradation of the insulation frame, is led to an insulation metal via the electric conductor, and a ground-fault relay is operated and a leakage electric current of the relay is detected, whereby an insulation degradation degree is grasped (for example, refer to Patent Document 2).